Sharpening, to buff or not to buff

C L Wilkins

C L Wilkins

Joined
Mar 18, 1999
Messages
2,112
Maybe this can be placed in the "Tip of the Day" category once it is answered.

I have seen where some folks will buff the edge on their blades after sharpening to get rid of the burr or wire edge. I have also heard some folks say never to do that and just strop it on it on leather. I have done both.

Any comments? Answers? Pros? Cons?

C Wilkins
 
I have two thoughts on this. Most customers expect a smooth razor edge on a knife, whether its done on a buff or a paper wheel, the results are the same. I also feel that a razor edge is not always the best edge to have on a "working" knife. When I use a knife in the field, I like the "bitey" edge that a 600 grit fine india stone provides. In head to head comparisons this type of edge will routinely outlast a razor edge in hunting type chores such as gutting, caping, and skinning.
I will usually do the buff thing on a customer's blade, because that is what they expect. Every now and again a customer will ask what type of edge I would put on, if it were my knife, and those end up with the "stoned" edge.
http://www.mtn-webtech.com/~caffrey

------------------
Ed Caffrey
"The Montana Bladesmith"


 
I use DMT hones, finishing off with the finest, then strop on a leather impregnanted with a chromium oxide (green) compound, and finish on leather. The strop is a handy strip from Lee Valley Tools, thick leather glued to each side, one for the compound, the other plain leather. The result is a razor edge lasts a good long time.
 
After I lay the edge over with a 320 grit belt, I white rouge all my blades. Makes em super smooth and super sharp.

------------------
"Always think of your fellow knife makers as partners in the search for the perfect blade, not as people trying to compete with you and your work!"


[This message has been edited by L6STEEL (edited 01 November 1999).]
 
I worry that while the edge may be sharp when it is finished with power tools, it may also be softer. A fine edge is all surface area and no real mass. Heat is put into the edge material proportional to the surface area (due to simple friction) and proportional to the mass of material removed (due to the work function of the metal). Heat gets out of the edge by conduction and convection. The heat conducts into the body of the blade and somewhat into the buffing wheel. The buffing wheel is not a good conduction medium, but at least it has a large surface that is spinning through air. Stainless alloys don't conduct heat real well and there is a very thin heat conduction path from the edge to the remainder of the blade.

So, does anyone else out there worry that an edge may not hold up as well if it is buffed?
 
Aren't most if not all of our blades buffed at some stage after heat treat regardless if the edge is buffed or not? I don't think I have ever gotten a finished blade hot enough during buffing where I was unable to hold it. Too hot to hold would have to be in the mid 100s. This definitely would not be a factor as far as degrading the temper goes. I don't believe that buffing would factor in...

C Wilkins
 
Guys: I buff my edges. But, I do it VERY lightly-almost no pressure. This removes the burr, after several passes per side, but, won't polish out all the scratches that give the edge "bite". I agree that, if you lean into the edge on the buffer, you can generate some tremendous heat, and, it has no place to go. ( Another good reason to use BG42, as it doesn't temper in the 300 F range.) But, the best thing is to go SLOW, and don't allow the heat to build up at all. You can also round off the edge TOO much by buffing too hard.
There are lots of ways to produce a sharp edge, and, there are many kinds of edges. I'd recommend experimenting with the grit belt you sharpen with, as well as how long you buff the finished edge, and, what compound you use. You'll develop an edge you like.

RJ Martin www.martinsite.com
 
CLW--
--Although you may be able to hold a blade when you buff or grind it, localized areas are much hotter than the blade at large. You never hold it on the same spot you are applying your belt or wheel. Stainless steel conducts heat slower than many other metals and is even more likely to get very hot in one spot and take a long time before the heat spreads out to where you are holding it. By the time it gets to your fingers the heat that began in a very small region of the material is spread over a larger mass of material and therefore the larger mass does not get up to as high a temperature. It is very common to burn an edge while grinding a blade. In that extreme case you can see the metal darken in localized spots on the edge.

It is arguable whether this happens when you are buffing. I assume that if it happens it is in a very small region right at the tip of the edge. If there were any tendency to discolor it would probably be obscured by the polishing effect of the buffing. This is why I solicited opinions. I have some experience with edges made with sanding disks that dulled very rapidly. I don't have much experience with buffing.
 
You must log in or register to reply here.
Back
Top